This option had been broken for several reasons:
* The getstyle utility does not replace the #usergnusteppath# macro which
was passed to it by the menu.
* When processing the USER_THEMES_DIR macro, the menu inserts a space
afterwards, and so the directory and filename were passed to getstyle
as two separate arguments.
* It used the old, pre-0.50.0 theme format.
By using the -p option to getstyle, we can avoid these issues, as we don't
need to specify the directory *and* it uses the 'new' (since 1999) themepack
format.
Compacting a translation to fit the available space; two new strings.
The menus are now split like the English ones, using appearance.menu.nl
and background.menu.nl. A new comment was added to menu.nl.in.
